Manning's n values for floodplains with shrubs and woody vegetation
Date
1998-10
Authors
Freeman, Gary E., author
Rahmeyer, William, author
Derrick, David L., author
Copeland, Ronald R., author
U.S. Committee on Irrigation and Drainage, publisher
Journal Title
Journal ISSN
Volume Title
Abstract
An improved methodology has been developed for the determination of Manning's n and other hydraulic roughness values for shrubs and woody vegetation. This method involves the measurement of horizontal plant density, stem diameter, and the height and width of the leaf mass of a typical plant. Recent investigation has shown that the plant stiffness modulus may be predicted with good accuracy by using stem diameter and plant height in a non-linear relationship. New relationships have been developed for the calculation of Mannings n values for both submerged and partially submerged vegetation. These relationships for flow through vegetated channels still require a trial and error solution when both depth and velocity are unknown, but simplify the solution technique significantly. A stage-discharge table can now be directly constructed for flood elevation studies without trial and error solutions. A simple example of the calculation of Manning's n values using the method is presented so that the practitioner can follow the method and apply it in the field.
Description
Presented at River basin management to meet competing needs: proceedings from the USCID conference on shared rivers held on October 21-31, 1998 in Park City, Utah.